All this data is potentially out of date, and should be taken with a truckload of salt
The Erebus titan is known for it's deep, almost black, coloration. It provides fleet members with a bonus to armor hitpoints, which can be useful when trying to survive a devastating doomsday activation. The ship is highlighted with green, similar to the rest of Gallantean design.
In greek mythology, Erebus is the son of the God Kaos. He is represented as the personification of darkness and shadow, filling in all areas of the world. Erebus was also the lover of Nyx, the name of the Gallantean mothership and the goddess of nightfall.